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Flume >> mail # user >> Guarantees of the memory channel for delivering to sink


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Re: Guarantees of the memory channel for delivering to sink
Ping on the below questions about new Spool Directory source:

If we choose to use the memory channel with this source, to an Avro sink on a remote box, do we risk data loss in the eventuality of a network partition/slow network or if the flume-agent on the source box dies?
If we choose to use file channel with this source, we will result in double writes to disk, correct? (one for the legacy log files which will be ingested by the Spool Directory source, and the other for the WAL)
________________________________
 From: Rahul Ravindran <[EMAIL PROTECTED]>
To: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
Sent: Tuesday, November 6, 2012 3:40 PM
Subject: Re: Guarantees of the memory channel for delivering to sink
 

This is awesome. 
This may be perfect for our use case :)

When is the 1.3 release expected?

Couple of questions for the choice of channel for the new source:

If we choose to use the memory channel with this source, to an Avro sink on a remote box, do we risk data loss in the eventuality of a network partition/slow network or if the flume-agent on the source box dies?
If we choose to use file channel with this source, we will result in double writes to disk, correct? (one for the legacy log files which will be ingested by the Spool Directory source, and the other for the WAL)

Thanks,
~Rahul.
________________________________
 From: Brock Noland <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]; Rahul Ravindran <[EMAIL PROTECTED]>
Sent: Tuesday, November 6, 2012 3:05 PM
Subject: Re: Guarantees of the memory channel for delivering to sink
 
This use case sounds like a perfect use of the Spool DIrectory source
which will be in the upcoming 1.3 release.

Brock

On Tue, Nov 6, 2012 at 4:53 PM, Rahul Ravindran <[EMAIL PROTECTED]> wrote:
> We will update the checkpoint each time (we may tune this to be
 periodic)
> but the contents of the memory channel will be in the legacy logs which are
> currently being generated.
>
> Additionally, the sink for the memory channel will be an Avro source in
> another machine.
>
> Does that clear things up?
>
> ________________________________
> From: Brock Noland <[EMAIL PROTECTED]>
> To: [EMAIL PROTECTED]; Rahul Ravindran <[EMAIL PROTECTED]>
> Sent: Tuesday, November 6, 2012 1:44 PM
>
> Subject: Re: Guarantees of the memory channel for delivering to sink
>
> But in your architecture you are going to write the contents of the
> memory channel out? Or did I miss
 something?
>
> "The checkpoint will be updated each time we perform a successive
> insertion into the memory channel."
>
> On Tue, Nov 6, 2012 at 3:43 PM, Rahul Ravindran <[EMAIL PROTECTED]> wrote:
>> We have a legacy system which writes events to a file (existing log file).
>> This will continue. If I used a filechannel, I will be double the number
>> of
>> IO operations(writes to the legacy log file, and writes to WAL).
>>
>> ________________________________
>> From: Brock Noland <[EMAIL PROTECTED]>
>> To: [EMAIL PROTECTED]; Rahul Ravindran <[EMAIL PROTECTED]>
>> Sent: Tuesday, November 6, 2012 1:38 PM
>> Subject: Re: Guarantees of the memory channel for delivering to sink
>>
>> Your still going to be writing out all events, no? So how would file
>> channel do more IO than that?
>>
>> On Tue, Nov 6, 2012 at 3:32 PM, Rahul Ravindran <[EMAIL PROTECTED]> wrote:
>>> Hi,
>>>    I am very new to Flume and we are hoping to use it for our log
>>> aggregation into HDFS. I have a few questions below:
>>>
>>> FileChannel will double our disk IO, which will affect IO performance on
>>> certain performance sensitive machines. Hence, I was hoping to write a
>>> custom Flume source which will use a memory channel, and which
 will
>>> perform
>>> checkpointing. The checkpoint will be updated each time we perform a
>>> successive insertion into the memory channel. (I realize that this
>>> results
>>> in a risk of data, the maximum size of which is the capacity of the
>>> memory
>>> channel).
>>>
>>>    As long as there is capacity in the memory channel buffers, does the
 is full because of lagging

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